Method of controlling the growth of undesirable vegetation



United States Patent O 3,413,109 METHOD OF CONTROLLING THE GROWTH OFUNDESIRABLE VEGETATION Joseph F. Vartiak, Naperville, Ill., assignor toNalco Chemical Company, Chicago, Ill., a corporation of Delaware NoDrawing. Continuation-impart of application Ser. No. 370,691, May 27,1964. This application Apr. 19, 1967, Ser. No. 631,904

The portion of the term of the patent subsequent to Dec. 26, 1984, hasbeen disclaimed 3 Claims. (Cl. 7165) ABSTRACT OF THE DISCLOSURE Thisinvention relates to a method of spraying oil solutions of herbicidalliquids in the presence of certain polymers whereby the misting anddrifting tendencies of these liquids are reduced.

This application is a continuation-in-part of my earlier filedapplication, Ser. No. 370,691, filed May 27, 1964, now US. Patent No.3,360,356.

The use of herbicides to control and inhibit undesirable weed growth iswell-known and of widespread usage in the agricultural, industrial, anddomestic fields, Roadsides, embankments, railway right-of-way, and otherearth surfaces are often subjected to treatment with toxic chemicals,organic and inorganic. Numerous compounds with widely variantfunctionalities are effective to a greater or lesser degree ininhibiting or destroying the growth of undesirable vegetation.

Noxious plants or weeds which interfere with human operations Ibroadlyinclude broad leaf plants and grasses. Herbicides have been tailored todestroy or inhibit the growth of both of these or a single group. Insome instances, mixtures of herbicidally active components are employedto combat various species of pervasive type plants.

One of the most widely used techniques in eradicating undesirable weedgrowth is accomplished by spraying the herbicidally active chemical uponthe area within which the plants are growing. In some instances,preemergence spraying is carried out. That is, suspected areas of weedgrowth are sprayed in early spring or late fall to prevent even anappearance of noxious plants or at the least to severely weaken theirgrowth patterns. One of the most effective Ways of carrying out a weedcontrol program is spraying the area under control from moving vehicles.As just one example, it is a common practice to spray railwayrights-of-way from a moving train.

Certain problems arise in connection with a herbicidal spray program.First, and foremost, is the problem of misting or fogging whichgenerally begins to occur at a spray pressure of p.s.i. and worsens asspray pressures are increased. The herbicidal spray tends to drift andmany valuable crops can be destroyed or damaged to varying degrees. Insome instances, due to extreme toxicity of certain herbicides, evenvaluable animal life such as livestock can be injured. The problem ofdrift has become more widespread in recent years, due to both the moreextensive use of herbicides, as well as application of these herbicidesas concentrated solutions in low volumes per acre.

Generally, undesirable drift from spraying of herbi- 3,413,109 PatentedNov. 26, 1968 cidal solutions may occur in two ways. First, spray driftmay occur as a result of the smaller droplets in the spray being carriedaway from the target by wind or convection currents. Second, the vaporfrom a volatile herbicide may be carried away from the target areaduring or after the spraying in a type of phenomenon called vapor drift.This is most likely to occur in hot weather and can take place even inthe absence of wind.

Etforts to substantially reduce spray and vapor drift have in the pastgenerally been unsuccessful or impractical. To minimize drift, sprayingmay be carried out only on days when there is negligible air movement.Such practice is impractical and substantially inhibits overallefficiency of a herbicidal control program. Likewise, efforts to reduceundesirable misting or fogging by specific design of nozzles has metwith only limited success, and even in such cases requires animpractical sophisticated mechanical design. Lowering the spray pressuredoes aid to some degree in preventing drift. However, sound econornicsof a herbicidal spraying operation consistent with good weed control donot allow too great a reduction in spray pressures.

It would therefore be a considerable advance in the herbicidal art if anew and novel method of spraying herbicidally active chemicals wasdevised, whereby undesirable drift was substantially reduced or evendone away with entirely as a problem. If a stream of herbicide chemicalcould be sprayed from solution form, on exact target without substantialmisting or fogging simultaneously taking place, considerable benefitswould accrue. Particularly, desirable animal and plant life could bepreserved without any decrease in efiiciency of eradicating noxiousvegetation. Moreover, if such method could be carried out withoutsacrificing operational speed of present herbicidal spray methods,widespread use of such an improved process would be feasible.Specifically, if spray techniques could be carried out at relativelyhigh pressures without fear of misting or fogging, it would be avaluable tool to the overall field or herbicide control. Lastly, if theproblem of misting or fogging were done away with in spraying herbicidesdissolved or dispersed in a variety of liquid hydrophobic carriers suchas oils, such versatile process would become widely adapted in anyconventional herbicide spray program.

It therefore becomes an object of the invention to provide an improvedmethod of spraying liquids whereby misting or fogging tendencies ofthese liquids are substantially reduced.

Another object of the invention is to provide an improved method ofinhibiting the growth and reproduction of noxious plants by sprayingherbicidal liquids within the area to be controlled.

A specific object of the invention is to provide an improved method ofinhibiting the growth and reproduction of noxious plants by sprayingherbicidal liquids within the area to be controlled.

A specific object of the invention is to provide an improved method ofspraying herbicidal liquid concentrates which may be adapted for use inspraying herbicides carried in hydrophobic type solvents.

Other objects will appear hereinafter.

In accordance with the invention an improved method of controlling thegrowth of undesirable vegetation has been discussed. In its broadestaspect this invention is involved with modification of the conventionalprocess of spraying with a solution containing a herbicidal component.The improvement of this process which constitutes the gist of theinvention comprises spraying a herbicidal solution in presence of apolymer which is soluble in a herbicidally active oil solution in atleast use dosages. Under such conditions the misting tendencies of theherbicidal liquid when sprayed are substantially reduced. Spray or vapordrift which normally occurs during a high pressure spray operation issubstantially reduced, and in some instances completely obviated.

An important concept of the invention is to carry out the primary objectof reducing misting or fogging of spray solutions by appropriateincorporation of polymer reagent, but without substantially increasingthe viscosity of the solution after polymer dissolution. It has beendiscovered that this can be accomplished in the practices of the instantinvention, since only relatively minute amounts of polymer need bepresent to accomplish the object of mist or fog control. If theviscosity of the polymer-treated herbicidal liquid is markedly increasedseveral drawbacks are inherently present. First, undesirable plugging ofherbicidal solution in spray nozzles may occur. Also, substantialviscosity increases of a treated herbicidal liquid would cause severepumping problems. Another deficiency in the use of viscous herbicidalconcentrates would be a marked decrease in volume of spray solution perunit of time which can be efficiently sprayed upon the situs to becontrolled. Other drawbacks in application of a viscous solution viaspray techniques will be apparent to those skilled in the art. It isthus a primary achievement in the invention to be able to carry out theanti-misting or anti-fogging control with relatively no increase insolution viscosity of herbicide solutions.

The process of the invention may be carried out via a wide variety ofdifferent techniques. For example, the polymer may be inter dispersedwith the spray from a separate polymer source during the actual sprayingoperation itself. Likewise, the polymer treating agent may be combinedwith the herbicidal liquid at the initial point of spraying byintroducing the polymer into the spray nozzle or even the nozzle orificefrom some outside reservoir. The most practical method of incorporationof polymer into herbicidal solution involves a treatment of the solutionprior to the actual spray step. The polymer is preferably dissolved inthe herbicidal solution and homogeneously dispersed throughout byconventional mixing techniques. This may be accomplished at any timeprior to spray breakdown of the herbicidal solution phase into actualspray droplets. One convenient method is to dissolve the polymer intothe herbicidal solution just immediately before application. Forexample, the actual mixing operation may be effected upon a movingvehicle such as a railroad car which is used to spray the particulararea to be controlled. It is understood, of course, that the herbicidalprocess of the invention may be carried out by either sprayingundesirable vegetation while in growth stage or spraying the groundprior to plant emergence.

Depending upon the nature of the polymer, its mo lecular configuration,molecular weight, etc., use dosages may be varied over a considerablerange. It is preferred that the viscosity of a hydrophobic or oil-basedsolution should not be increased more than 100 centipoises. With theabove points in mind, generally in the most preferred practice of theinvention from about 10 to about 3000 p.p.m. of high molecular weightpolymer are added to the herbicidal liquid. Within this range, mistingor fogging is at the very minimum substantially reduced. In someinstances such undesirable phenomenon has been completely corrected. Thetarget of the herbicidal solution thus reaps the exclusive benefit ofherbicidal control without undesirable side effects of injury to cropsand desirable plant species. Likewise, fear of injury to animals who mayfeed upon herbicidally contacted non-target vegetation may be done awaywith by following the thus described invention.

The anti-misting polymer may be added to any type of solution containinga wide variety of herbicidally active chemicals. These chemicals aregenerally applied in solution form in one of the following liquid forms:oil and water-in-oil emulsions.

The term oil solution means a herbicidal liquid containing a hydrocarbonconstituent as the primary component, and includes water-in-oilemulsions. Such oil solutions normally contain at least by weight of oiland more often by weight. If such a system is to be treated with ananti-fogging polymer, it is again greatly preferred that the polymer besoluble in the oil or hydrocarbon phase to achieve best results. Theoil-based herbicidal liquid may contain minor amounts of other solventsor additives such as organic solvents, for example, alcohols, ketones,esters, etc. Emulsifying agents, surfaceactive chemicals, dispersingaids, etc., may also form a portion of the herbicidal solution. Forexample, detergent-type wetting agents may be employed, as for example,those described in the article entitled Detergents and Emulsifiers byJohn W. McCutcheon, 1963.

Oil-containing herbicidal solutions as straight oil solutions andwater-in-oil emulsions, may be made of a variety of hydrocarbons orpetroleum products such as kerosene, mineral oil, naphthas, gas oils,crude oil, light distillates, etc. In many instances the hydrocarbon oilcarrier for the herbicide is itself phytotoxic in nature. In particular,it has been found that those hydrocarbons that are best for providingoil-based herbicidal concentrates, which may be subsequently treatedwith anti-misting polymer, are hydrocarbon oils which may be genericallyclassified as aromatic petroleum hydrocarbon solvents. Specifically,this type of solvent includes those particular petroleum type solvents"which contain at least 5% by weight of aromatic components and mostpreferably, 50% by weight or more. Examples of solvents of this type arelisted in Table I below. For convenience, the specifications of thesetypical industrial aromatic type oils are included.

TABLE I Compositions Specifications C D E F G Specific gravity at 60 FFlash point PMCC F.)

Aromatics and oofius (percent) 45-48 Color ASTM 1.5 Aniline point, 117Four point, F. 5 Sulfur (percent) 0.8 Viscosity S.U. at 100 F. ASTMDistillation 36 1.13.1. F 430 10% recovered 485 50% recovered. 525recovered. 587 End point 620 Pentachlorophenol solution at 40 F.(percent) 12. 5

1 Pole amber. 1 Deg. C. 3 Mixed.

The most effective oil-based herbicidal liquids which may be treated inthe instant invention contain oils which have an aromatic content of atleast 50% and more preferably from 70 to 85% by weight.

The invention is adaptable to spraying a vast number of known herbicideswhich are soluble, dispersible, or emulsifiable in hydrocarbon solventsor emulsions thereof. Specific herbicidal liquid concentrates which maybe sprayed in the presence of high molecular weight polymer include thefollowing representative classes; such as substituted uracils as 5 bromo3 sec. butyl-methyl uracil, such aryl alkyl urea herbicides as 1phenyl-3- methylurea, 1 (3 chloro 4 methoxy-phenyl)-3,3- dimethylurea, l(3 chlorophenyl) 3,3 dimethylurea, 1 (3,4 dichlorophenyl) 3,3dimethylurea, and lphenyl 3,3 dimethylurea; acidic herbicides such as2,4- dichlorophenoxyacetic acid, 2 methyl 4 chlorophenoxyacetic acid,2,4,5 trichlorophenoxy-acetic acid, 3,4- dichlorophenoxyacetic acid, 4chlorophenoxyacetic acid, 2 (2,4 dichlorophenoxy) propionic acid, 2(2-methyl- 4 chlorophenoxy) propionic acid, 2 2,4,5 trichlorophenoxy)propionic acid, 2 (3,4 dichlorophenoxy) propionic acid, 2 (4chlorophenoxy) propionic acid, 4 (2,4 dichlorophenoxy) butyric acid, 4(Z-methyl- 4-chlorophenoxy) butyric acid, 4 (2,4,5 trichlorophenoxy)butyric acid, 4 (3,4 dichlorophenoxy) butyric acid, 4 (4 chlorophenoxy)butyric acid, trichloroacetic acid, 2,2 dichloropropionic acid, 2,2,3trichloropropionic acid, 2,3,6 trichlorobenzoic acid, 2,3,5,6tetrachlorobenzoic acid, N-l-naphthylphthalamic acid, 2,6-endoxohexahydrophthalic acid, isopropyl xanthic acid,

monomethylarsonic acid, polychlorobenzoic acid, such substitutedpicolinic acids as 4 amino 3,5,6 trichloro picolinic acid andphentachloro pentadienoic acid; salts, esters, amides of any of theforegoing herbicidal acids or others; maleic hydrazide and itsherbicidal derivatives; polychlorophenols (3 to 5 chlorine atoms) andtheir alkaline salts; sulfamic acid and its salts; alkaline salts ofcyanic acid; alkaline salts of thiocyanic acid; alkaline salts ofarsenous and arsenic acids; sodium borates; sodium or calcium cyanamide;phenyl mercury salts (acetate, oleate, formate, lactate, chloride,phosphate, and the like); isopropyl esters of phenylandchlorophenylcarbamie acids; 1,2,4 trichlorobenzene; dinitrophenols(dinitro-o-cresol and dinitro-o-butylphenol) and their salts; borontrifiuoride amine complexes; amino substituted s-triazines such as 2chloro 4,6 bis (ethylamino)- s-triazine, 2 chloro 4, ethylamino 6,isopropylamino-striazone, 2 methoxy 4,6 bis (isopropylamino)-s-triazine,2 chloro-4,6-bis (diethylamino)-s-triazine, etc., and variouscombinations of the just mentioned herbicides and others.

The oil-soluble mist-decreasing polymers of the invention should have amolecular weight of at least 25,000. Preferably the molecular weight isin excess of 100,000.

It is greatly preferred that the polymeric anti-fogging agent be solublein the oil component. It is, therefore, preferable that the polymer bederived from a hydrophobic monomer. Examples typical of these arestyrene, alpha-methylstyrene, vinyl toluene, chlorostyrene, vinylacetate, vinyl chloride, vinyl formate, vinyl alkyl ethers, alkylacrylates, alkyl methacrylates, ethylene, propylene, n-butylene,isobutylene, etc. The most preferred oilsoluble polymers have amolecular weight in excess of 100,000. These polymers which have shownthe greatest measure of success have a linear hydrocarbon structurederived from an ethylenically unsaturated monomer containing 2-5 carbonatoms. These monomers may contain one or two unsaturated groups. Amongthese, polyethylene, polypropylene, polyisobutylene, polybutadiene,polyisoprene and copolymers thereof have shown the most promise.Polyisobutylene and polyisoprene (natural rubber) are the most preferredof this group.

By the term soluble, as applied to the property of the polymers of theinvention of being able to be incorporated into herbicide solutions, ismeant the ability of being solubilized or dispersed in at least useamounts in the liquid being treated.

It is not totally understood how the just mentioned polymers or othersfalling within the defined group of workable materials aid insubstantially reducing misting or fogging of sprayed solutions even whenapplied in relatively minute amounts. Without polymer present during aspraying operation a pressure drop occurs in which excess energy presentactually fractures the liquids into mist or fog. When the polymer isadded to the sprayed solution it is believed a visco-elastic effecttakes place. That is to say, the polymer-treated liquid actually isdeformed in a visco-elastic manner which allows the energy from thepressure drop to fracture the liquid in a more uniform manner, andprevent the formation of very small droplets. This occurs rather thanthe spray breaking up into a mist pattern. In essence, shock or energyis taken up by a polymer-treated liquid in contradistinction to anuntreated solution which is incapable of resisting the shock or energywithout substantially changing its rheological characteristics.

It was noted that in spraying polymer treated herbicidal solutions andother treated solutions, a variety of advantages other than mistreduction are present. For example, uniformity of spray pattern as wellas droplet size is achieved. In addition, concentration of spraypressure at point of impact is increased.

Example I A herbicidal oil solution was made up containing the followingdescribed components. The oil was itself phytotoxic in nature andcontained approximately 45% aromatics. Into this oil was dissolved 1.9%of the propylene glycol butyl ether ester of 2,4,5-trichlorophenoxyacetic acid. This particular herbicidal oil solution was tested in afield application, and specifically sprayed upon dormant brush growingalong a roadside. Without benefit of polymer treatment, it was notedthat the spray blew in a wide pattern, and even across the entire roadwidth. With an incorporation of approximately 400 p.p.m. of apolyisobutylene polymer having a molecular weight of approximately350,000, a thus treated oil solution containing the above herbicidecomponents was sprayed in a comparative application. In this instance adefinite reduction in drift was noted and at no time did the spray blowany appreciable distance.

Example II Into the oil described in Example I was dissolved 3.4% of theisooctyl ester of 2-(2,4,5-trichlorophenoxy) propionic acid herbicide.This oil solution was again sprayed with and without benefit ofpolyisobutylene (molecular weight=300,000; 400 p.p.m. treatment level).The same results were noted as set out in Example I.

The above examples are intended to illustrate the process of theinvention, and are not intended to be li-mitati've thereof. Othermodifications and variations of the invention will be apparent to thoseskilled in the art.

The invention is hereby claimed as follows:

1. A method of controlling the growth of undesirable vegetation whichcomprises the steps of spraying oil solutions which contain (a) aphytotoxic amount of a herbicide, and

(b) dissolved therein at least 10 parts per million but yet asubstantially non-viscosity increasing amount of a polymer formed by thepolymerization of at least one monoolefinic compound through analiphatic unsaturated group and having a molecular weight of at least25,000,

said liquid being characterized as having reduced misting tendencieswhen sprayed.

2. The method of claim 1 where the molecular weight of the polymer is atleast 100,000.

3. The method of claim 2 wherein the viscosity is not 7 increased bymore than 100 centipoises over the viscosity of the untreated solution.

References Cited 3,067,089 12/1962 Winslow 167-42 Beerbouer et a1.167-42 Seymour et a1. 712.7

Seymour et a1. 7l2.6

Littler 712.2 X

Fordyce 167-22 JAMES O. THOMAS, JR., Primary Examiner.

